Re: contouring station data

James,

You have some conflicting information in your script that might be
causing a problem.

First you have:

    res_at_tfDoNDCOverlay = True

which tells NCL that the data has already been projected onto a
particular map projection, so no calculations will be done to
transform your data to the given map projection. This setting
only works if you know the *exact* projection your data
was measured on. And, given that you are calling WRF_mapres_c,
this is supposed to set up your map resources to set up
the correct map projection.

But, then you have:

   res_at_mpRightCornerLonF = lona(y2,x2)
   res_at_mpRightCornerLatF = lata(y2,x2)
   res_at_mpLeftCornerLonF = lona(y1,x1)
   res_at_mpLeftCornerLatF = lata(y1,x1)

This is effectively changing the map projection to something different
than what your data were actually measured, on, so now your data will
probably not look correct.

Finally, you have:

   res_at_sfXArray = lon
   res_at_sfYArray = lat

I'm not sure where the "lon" and "lat" variables came from,
but these should probably be "lata" and "lona", if anything.
You don't want to set sfXArray/sfYArray if you've
set tfDoNDCOverlay to True.

To fix all of this, please try the following steps:

Remove or comment out the line:

    res_at_tfDoNDCOverlay = True

(The default of this resource is False).

Change the following "if" statement:

  if (.not.res_at_tfDoNDCOverlay) then
      lat2d = f->XLAT(0,:,:) ; need for map limits
      lon2d = f->XLONG(0,:,:)
  end if

to:

  if (.not.res_at_tfDoNDCOverlay) then
      cp_at_lat2d = f->XLAT(0,:,:) ; need for map limits
      cp_at_lon2d = f->XLONG(0,:,:)
  end if

The gsn_csm_xxx_map scripts recognize the special "lat2d"
and "lon2d" attributes and will use these to determine where
on the map your data is projected. Hence, you no longer need to
worry about getting the map projection exactly right.

Finally, remove or comment out the lines:

; res_at_sfXArray = lon
; res_at_sfYArray = lat

These two lines will be handled for you internally by virtue of
setting the special lat2d/lon2d attributes.

Hope this all makes sense.

--Mary

On Wed, 22 Oct 2008, James Correia wrote:

> All-
> I am having trouble getting my station data to conform to the projection I
> am using. I can use the gsn_add_text function to overlay numbers, but when I
> contour the data, the data are shifted relative to the map (looks more like
> "triangularmesh" assumes the grid is a rectangle, than actually transforming
> the lat-lon locations to match the LambertConformal projection).
>
> Perhaps an alternative is to use rgrid2rcm?
>
> jimmyc
>
> below is the relevant code.
> wks = gsn_open_wks("ps" ,"freq") ; ps,pdf,x11,ncgm,eps
> gsn_define_colormap(wks ,"BlAqGrYeOrReVi200"); choose colormap
>
> res = True ; plot mods desired
> res_at_gsnMaximize = True ; uncomment to maximize size
> res_at_gsnSpreadColors = True ; use full range of colormap
> res_at_cnFillOn = True ; color plot desired
> res_at_cnLinesOn = False ; turn off contour lines
> res_at_cnLineLabelsOn = False ; turn off contour labels
> res_at_lbLabelAutoStride = True ; let NCL figure lb stride
> res_at_cnLevelSelectionMode = "ExplicitLevels" ; explicit [unequal] cn
> levels
>
> res_at_cnLevels = (/10,20,30,40,50,60,70,80,90/)
> ;************************************************
> ; Use WRF_contributed procedure to set map resources
> ;************************************************
> WRF_map_c(f,res,0) ; set map resources
> ;************************************************
> ; set True for native mapping (faster plotting)
> ; set to False othewise
> ;************************************************
> res_at_tfDoNDCOverlay = True
>
> ;************************************************
> ; associate the 2-dimensional coordinates to variables for plotting
> ; only if res_at_tfDoNDCOverlay=False
> ;************************************************
> if (.not.res_at_tfDoNDCOverlay) then
> lat2d = f->XLAT(0,:,:) ; need for map limits
>
> lon2d = f->XLONG(0,:,:)
> end if
>
>
> ;************************************************
> ; allocate array for 3 plots
> ;************************************************
> plot = new (1,"graphic")
> ;************************************************
>
>
> lata = f->XLAT(0,:,:)
> lona = f->XLONG(0,:,:)
> ;x2 = 105
> ;y2 = 80
> ;x1 = 43
> ;y1 = 18
> x2 = 100
> y2 = 85
> x1 = 38
> y1 = 22
> ;x2 = 143
> ;y2 = 118
> ;x1 = 10
> ;y1 = 10
>
> res_at_mpRightCornerLonF = lona(y2,x2)
> res_at_mpRightCornerLatF = lata(y2,x2)
> res_at_mpLeftCornerLonF = lona(y1,x1)
> res_at_mpLeftCornerLatF = lata(y1,x1)
>
> ;************************************************
> ; Tell NCL not to draw or advance frame for individual plots
> ;************************************************
> ; res_at_gsnDraw = False ; (a) do not draw
> ; res_at_gsnFrame = False ; (b) do not advance 'frame'
> res_at_trGridType = "TriangularMesh" ; The default if you
> ; have 1D data
> res_at_sfXArray = lon
> res_at_sfYArray = lat
> print(res)
>
> res_at_gsnLeftString ="CAPE 500 J kg-1"
> ;plot(0) = gsn_csm_map(wks,res)
> print(cp)
> plot = gsn_csm_contour_map(wks,cp,res)
>
> --
> James Correia Jr.
> Post Doc
> Climate Physics Group, PNNL
>
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Received on Wed Oct 22 2008 - 13:46:41 MDT